JP2009159454A - Solid-state imaging device - Google Patents

Abstract

An object of the present invention is to reduce a period in which a captured image is overexposed or underexposed even when suddenly entering a bright place or a dark place during photographing.
A driver unit that generates an electronic shutter pulse having a required voltage based on a shutter instruction signal, and imaging data is read in synchronization with a vertical synchronization signal, and the next time the integrated result of the imaging data for one frame is read. In a solid-state imaging device including a solid-state imaging device in which the application end timing of an electronic shutter pulse at the time of a vertical synchronization signal is determined, depending on a result during the integration of one frame of imaging data read in synchronization with the current vertical synchronization signal Control means for outputting a shutter instruction signal to the driver means and controlling an electronic shutter pulse at the time of the current vertical synchronization signal is provided.
[Selection] Figure 3

Description

  The present invention relates to a solid-state imaging device that determines an exposure time using an electronic shutter pulse.

  FIG. 4 is a timing chart of electronic shutter control performed by a solid-state imaging device such as a conventional digital camera. When shooting a moving image with a digital camera or displaying a through image on a liquid crystal display provided on the back of the camera, a readout signal is applied to the solid-state image sensor for each vertical synchronization signal, and solid-state imaging is performed for each readout signal. Imaging data is read from the element.

  In the example shown in the drawing, the imaging data for one frame read from the solid-state imaging device by the readout signal 4 is data captured in the exposure period C immediately before the readout signal 4. This exposure period C is a period from the application end timing of the electronic shutter pulse c applied to the solid-state imaging device after the readout signal 3 to the application timing of the readout signal 4, and the application end of the electronic shutter pulse c is finished at what timing. This is determined by the camera control unit based on the imaging data for one frame in the exposure period A read by the read signal 2 immediately before.

  In the conventional solid-state imaging device, for example, as described in Patent Documents 1 and 2 below, the camera control unit calculates the exposure amount by integrating the imaging data for each frame by the AE operation, and according to the exposure amount. Thus, the electronic shutter period, that is, the application end timing of the electronic shutter pulse is determined. The camera control unit sets the determined electronic shutter pulse control signal in the timing generator of the image sensor driving unit, and controls the electronic shutter pulse applied to the solid-state image sensor by the timing generator.

JP 2000-125186 A Japanese Patent Laid-Open No. 2003-163832

  In the conventional solid-state imaging device, for example, when the imaging data in the exposure period A read by the readout signal 2 in FIG. 4 is too bright, the result of integrating the imaging data is reflected and the opening period of the electronic shutter is shortened by 1 The electronic shutter pulse c after the elapse of the vertical synchronization signal is obtained. For this reason, when you suddenly enter a bright place during shooting, there will be a period when the screen will be mostly overexposed (overexposed), or when you suddenly enter a dark place, most of the screen will be blacked out. There is a problem that a period during which the image becomes underexposed (underexposure) occurs.

  An object of the present invention is to provide a solid-state imaging device capable of reducing the above-described overexposure and underexposure periods even when suddenly entering a bright place or dark place during photographing.

  The solid-state imaging device according to the present invention includes a driver unit that generates an electronic shutter pulse having a required voltage based on a shutter instruction signal, reading of imaging data in synchronization with a vertical synchronization signal, and integration of the imaging data for one frame. In the solid-state imaging device including a solid-state imaging device that determines the application end timing of the electronic shutter pulse at the time of the next vertical synchronization signal based on the result, the one frame of the imaging data read in synchronization with the current vertical synchronization signal And a control means for outputting the shutter instruction signal to the driver means according to a result during the integration of minutes and controlling the electronic shutter pulse at the time of the current vertical synchronization signal.

  When the control means of the solid-state imaging device of the present invention determines that the result during the integration exceeds the specified luminance level and is too bright, after the application of the electronic shutter pulse at the time of the current vertical synchronization signal, again, The electronic shutter pulse is applied to the solid-state imaging device.

  When the control means of the solid-state imaging device of the present invention determines that the result during the integration is below a specified luminance level and is too dark, the electronic shutter pulse at the time of the current vertical synchronization signal is applied to the solid-state imaging device. The application is forcibly stopped halfway.

  According to the present invention, the control means directly controls the driver means without going through the timing generator to control the application of the electronic shutter pulse to the solid-state image sensor, so that the time required for the AE operation can be shortened. It becomes.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a functional block diagram of a solid-state imaging device according to an embodiment of the present invention. This solid-state imaging device 10 converts a subject optical image formed on a light receiving surface into an electrical signal and outputs it as imaging data, and an AFE / that performs analog processing on imaging data output from the solid-state imaging device 11. A TG (analog front end / timing generator) circuit 12 and imaging data, a horizontal synchronization signal (HD), and a vertical synchronization signal (VD) that have been analog processed and converted into digital data are received from the AFE / TG circuit 12 and image processing is performed. A DSP / CPU (digital signal processor / central processing unit) 13, a V driver 14, and a selector 15 are provided.

  For example, in a CCD (charge coupled device) type, the solid-state imaging device 11 operates by a vertical (V) transfer pulse, a horizontal (H) transfer pulse, an OFD (overflow drain) pulse, an electronic shutter pulse, a readout pulse, or the like.

  Since the horizontal (H) transfer pulse may be a low voltage of about 3.3 V, for example, the AFE / TG circuit 12 generates and directly outputs it to the solid-state image sensor 11 to control the horizontal charge transfer path of the solid-state image sensor.

  However, since the vertical (V) transfer pulse is, for example, -8V and the readout pulse is, for example, + 15V, the voltage is converted to a required high voltage via the V driver 14 and then output to the solid-state imaging device 11. ing. Since the OFD pulse and the electronic shutter pulse are also at a high voltage, they are output to the solid-state image sensor 11 via the V driver 14.

  The AFE / TG circuit 12 generates an original signal that becomes a vertical (V) transfer pulse and an original signal of an OFD pulse, and outputs the original signal of the vertical transfer pulse to the V driver 14. Conventionally, the AFE / TG circuit 12 also generates the original signal of the electronic shutter pulse. However, in the solid-state imaging device 10 of the present embodiment, the DSP / CPU 13 generates the original signal (shutter instruction signal) of the electronic shutter pulse. The data is output from a general purpose (global purpose) I / O of the DSP / CPU 13. That is, in the present embodiment, the electronic shutter pulse applied to the solid-state image sensor 11 is configured to be directly controlled by the DSP / CPU 13.

  The selector 15 selects one of the original signal of the OFD pulse generated by the AFE / TG circuit 12 and the original signal of the electronic shutter pulse generated by the DSP / CPU 13 and inputs the selected signal to the V driver 14.

  FIG. 2 is a flowchart showing a control procedure in which the DSP / CPU 13 outputs the original signal of the electronic shutter pulse. The DSP / CPU 13 integrates the imaging data received from the AFE / TG circuit 12 (step S1), and determines whether the result during the integration is smaller than a prescribed low luminance level (step S2).

  If the imaging data in the middle of integration is smaller than the prescribed low luminance level, that is, if the imaging data is too dark and the determination result is affirmative (YES), the process proceeds to step S3, and details will be described later. The electronic shutter signal currently being output is forcibly stopped, and the electronic shutter application end timing after the next vertical synchronization signal is determined based on the integration result of the imaging data for one frame, and the process returns to step S1.

  If the determination result in step S2 is negative (NO), that is, if the imaging data in the middle of integration is brighter than the specified low luminance level, the process proceeds from step S2 to step S4. Determine if greater than.

  If the imaged data in the middle of integration is larger than the specified high luminance level, that is, if the imaged data is too bright and the determination result is affirmative (YES), the process proceeds from step S4 to step S5, and details will be described later. In this manner, the electronic shutter signal that is currently stopped is output again, and the electronic shutter application end timing after the next vertical synchronization signal is determined based on the integrated value for one frame, and the process returns to step S1.

  If the determination result in step S4 is negative (NO), that is, if the image data is between the specified low luminance level and the high luminance level and the image data is not too dark and not too bright, the process proceeds from step S4 to step S6, and the next The electronic shutter application end timing after the vertical synchronization signal is determined based on the integration result of the image data for one frame, and the process returns to step S1.

  FIG. 3A is a timing chart for explaining the re-output of the electronic shutter executed in step S5 of FIG. For example, when a user on a train turns on the digital camera to take a picture of an outside landscape, the outside landscape image is displayed as a through image on the liquid crystal display unit on the back of the digital camera.

  The application end timing of the electronic shutter b applied to the solid-state imaging device 11 after the readout signal 2 shown in FIG. 3A is determined by the integrated value of the imaging data for one frame in the exposure period A immediately before the readout signal 2. Is done. The imaging data to be integrated is the imaging data in the exposure period x immediately before the previous readout signal 1.

  It is assumed that the train suddenly enters a sunny place from a shaded place between the readout signal 1 and the readout signal 2. Since the electronic shutter b is determined in the shaded state of the exposure period x, the application end timing of the electronic shutter b is set earlier in order to increase the open period of the electronic shutter b.

  However, when the train suddenly enters the sun, the imaging data in the exposure period A becomes high brightness. The high-brightness imaging data is read from the solid-state imaging device 11 by the readout signal 2, and is output sequentially from the AFE / TG circuit 12 to the DSP / CPU 13 each time it is read out, and is integrated in step S1 of FIG. Since it is found in step S4 that even the integrated value before the integration for one frame is completed, the image data is too bright, the DSP / CPU 13 sets the electronic shutter b ′ to V after the already stopped electronic shutter b. Output from the driver 14 to the solid-state imaging device 11.

  As a result, the exposure period B is shortened to a period from the application end timing of the electronic shutter b ′ to the readout signal 3, and the period in which the image is properly exposed without whiteout is accelerated by one vertical synchronization signal period compared to the conventional case. .

  FIG. 3B is a timing chart for explaining the forcible stop of the electronic shutter executed in step S3 of FIG. It is assumed that the train suddenly enters a shaded place from a sunny place between the readout signal 1 and the readout signal 2. Since the electronic shutter b is determined in the sunny state of the exposure period x, the application end timing of the electronic shutter b is set late in order to shorten the open period of the electronic shutter b.

  However, when the train suddenly enters the shade, the imaging data in the exposure period A becomes low brightness. This low-brightness imaging data is read from the solid-state imaging device 11 by the readout signal 2, and is output sequentially from the AFE / TG circuit 12 to the DSP / CPU 13 each time it is read out, and is integrated in step S1 of FIG. Since it is known in step S2 that the image data is too dark from the intermediate integrated value even before the integration for one frame is completed, the DSP / CPU 13 forcibly stops the electronic shutter b being output at timing b '.

  As a result, the exposure period B becomes longer from the application end timing of the electronic shutter b ′ to the readout signal 3, and the period during which an appropriate exposure is obtained without causing the image to be blacked out is a period of one vertical synchronization signal as compared with the conventional case. Speed up.

  As described above, in the solid-state imaging device according to the present embodiment, the electronic shutter pulse generation instruction is directly performed by the control unit that integrates the image data, so even if the image is suddenly moved to a bright place or a dark place. An image with appropriate exposure can be obtained at high speed, and the speed of the AE operation can be increased.

  Since the CPU used as the control unit usually has a counter and has I / O for various outputs, diverting them can avoid an increase in cost and perform the above-described AE operation of the solid-state imaging device. It is possible to increase the speed.

  According to the present invention, it is useful to apply to a digital camera because an image with a proper exposure can be taken immediately even when suddenly moved to a bright place or moved to a dark place.

It is a functional block diagram of the solid-state imaging device concerning one embodiment of the present invention. 3 is a flowchart showing an electronic shutter control procedure executed by the DSP / CPU shown in FIG. It is a timing chart which shows the mode of the electronic shutter control by the control procedure shown in FIG. It is a timing chart which shows the mode of the electronic shutter control by the conventional control procedure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Solid-state imaging device 11 Solid-state image sensor 12 AFE / TG circuit 13 DSP / CPU
14 V driver 15 selector

Claims (3)

  A driver means for generating an electronic shutter pulse of a required voltage based on a shutter instruction signal, and imaging data are read out in synchronization with the vertical synchronization signal, and at the next vertical synchronization signal based on the integration result of one frame of the imaging data. In the solid-state imaging device including the solid-state imaging device in which the application end timing of the electronic shutter pulse is determined in accordance with the result of the one-frame integration of the imaging data read in synchronization with the current vertical synchronization signal A solid-state imaging device comprising: control means for outputting a shutter instruction signal to the driver means to control the electronic shutter pulse at the time of the current vertical synchronization signal.   When the control means determines that the result during the integration exceeds a specified luminance level and is too bright, after the application of the electronic shutter pulse at the time of the current vertical synchronization signal is completed, the control unit again sets the electronic shutter pulse to the solid state. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is applied to an imaging device.   The control means forcibly stops the application of the electronic shutter pulse to the solid-state image sensor at the time of the current vertical synchronization signal when it is determined that the result during the integration is below a specified luminance level and is too dark. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is provided.

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